Default [Q] video switches to SW mode

I have a Le Pan S tablet (http://www.lepantab.com/index.php?op...d=88&Itemid=95) that works great for the first little while (20-40 minutes) when I play local video files. Then the player (both BS and MX with correct codecs) switches to software decoding from hardware, and the lag begins. I am trying to find out why it switches. Is it overheating? Something must be going wrong and it's very annoying. Thanks.